1. Field of the Invention
The present invention relates to tape rule with a tape of enhanced stiffness, and in particular, to a tape with stiffness increased to such an extent that the tape is able to keep straight up to 10.5 feet length without flexing when being drawn out.
2. Description of the Prior Art
The tape rule is a very widely used measurement rule from amateur and professional carpentry to civil and architectural survey work.
To keep reliable accuracy for measuring results, the tape shall be satisfactorily stiff when it is drawn out to a length, for example, about 8.5 feet. In a conventional tape rule, its tape is usually yield to flex when the extracted hanging length exceeds 8.5 feet so that dependable measuring data can not be obtained. There has been a tape rule with a tape of improved stiffness disclosed in the U.S. Pat. No. 6,324,769. The cambered transverse cross sectional surface has the dimension of width 27.94xcx9c38.1 mm , thickness 0.114xcx9c0.16 mm, cambered height 6.35xcx9c10.16 mm. With this structure, the tape can maintain required stiffness up to 10.5 ft extracted length accompanied with extra material and production costs and increased market price in compensation. Besides, excessive tape width causes the user hard to grasp that resulting in inconveniency to regular handling.
In order to solve the above described problems, the present inventor has carried long term theoretical studies and simulating experiments. Based on these studies and researches, the present inventor has come to propose the present invention.
Therefore, it is an object of the present invention to provide a tape rule with a tape of enhanced stiffness whose tape can be pulled out up to 10.5 feet long in hanging state without loosing its stiffness for measuring accuracy and made with small production cost so as to bring down the market price and stimulate the user""s desire to use.
It is another object of the present invention to provide a tape rule with a tape of enhanced stiffness whose tape is ingeniously constructed for easy handling.
For achieving the above objects, the transverse cross section of the tape according to the present invention is configurated in a V shape cambered surface of with 27 mm, thickness 0.11 mm, and cambered height measured from both terminals vertically to the tangential plane to the lowest point of the V shape cambered cross sectional surface. The tape is wound back and put away in a housing by a rewinding core spring of width 22 mm, thickness 0.12 mm, and length 4500 mm. With this structure, the whole tape rule is able to maintain perfect stiffness when being extracted up to 10.5 feet long suspending horizontally in the air with less material and production costs than that of a tape rule made according to conventional techniques.